The invention relates to a method in accordance with the preamble of patent claim 1. Such a method is disclosed in DE 39 14 697 C2 corresponding to U.S. Pat. No. 5,355,170 issued Oct. 11, 1994 to Gerhard Eitz.
In the conventional teletext system used at present in Europe, use is made of the so-called "Level 1" of the WST (World System Teletext) teletext standard, which permits texts and graphic representations to be represented with a restricted basic character set on a screen, on a page which consists of a head row and 23 rows.
As disclosed in DE 39 14 697 C2, in addition to these pages Level 1 can be used to transmit further supplementary data for special characters, fine structures and colour shadings. In addition to the desired Level 1 page, the associated supplementary data are intermediately stored at the receiving end and displayed together with the relevant Level 1 page on the screen.
Furthermore, for the purpose of programming a video recorder it is known from EP 0 214 326 for hidden program identifiers with an enhanced error protection to be transmitted in teletext pages in addition to the information represented visibly. The viewer marks the desired program on a program listing page and thus selects the associated program identifier for the recording. The program identifier, which additionally contains further code numbers for the respective program source and the calendar date, uniquely identifies a program and is transmitted together with a program. The video recorder starts to record when the preprogrammed program identifier matches that just detected. With such event-controlled recording, temporal shifts and interruptions etc. remain without effect on the recording, since the video recorder can react appropriately. In the event of cancellation of a program, an unnecessarily long "lurking" of the video recording can be avoided by transmitting a special cancellation identifier instead of the program identifier.
Furthermore, it is known from EP 0 264 565 B1 to use special pages to transmit information on the teletext pages currently being transmitted and evaluate it at the receiver end. By evaluating the special page in the receiver, it is possible to check whether a teletext page desired by the user has been transmitted at all, to select the teletext pages without unnecessary waiting time and to use the available decoder memory in an optimum fashion.